Subject: Re: [Boost-users] make member functions (in)accessible
From: dhruva (dhruva_at_[hidden])
Date: 2009-02-26 09:08:56
Though I have not used it myself, there is enable_if or disable_if in BOOST. That might help.
-dhruva
----- Original Message ----
> From: Stefan Funck <stefanfunck_at_[hidden]>
> To: boost-users_at_[hidden]
> Sent: Thursday, 26 February, 2009 7:34:01 PM
> Subject: [Boost-users] make member functions (in)accessible
>
> Dear all,
>
> I'm trying to find some magic that makes a member function of some object x
> accessible if and only if it were called from within a class that has object x
> as a member. Is there a (boost)-way of doing this?
>
> As this may seem a bit obscure, I'm trying to give an example:
>
> template
> class Property
> {
> public:
> T get() const;
> void set(const T& val);
> private:
> T m_val;
> };
> is a simple class holding a value of T.
>
> I have some classes holding potentially many Properties. I'd like to have these
> properties publically available, some as only readable, others writable as well,
> so that others (e.g. gui-classes) can access them:
>
> class A
> {
> public:
> Property propA;
> Property propB;
> };
>
> so I may do:
>
> A a;
> a.propA.get();
> a.propA.set(0.5);
> a.propB.get();
>
> but NOT:
>
> a.propB.set(1);
>
> because propB was defined with Writable=false. BUT, from within class A, I would
> like to do
>
> propB.set(1);
>
> because otherwise this property is useless. (How) can this be achieved (with
> boost)?
>
> I could make set() private in the Writable=false - specialisation of Property
> and declare A as a friend, but that's prohibitive since Property shouldn't know
> about A and it won't work for derived classes of A. Another option would be
>
> class A
> {
> public:
> A() : propA(propA_priv), propB(propB_priv) {}
>
> PropertyWrapper propA;
> PropertyWrapper propB;
> private:
> Property propA_priv;
> Property propB_priv;
> };
>
> so the actual properties are private and the wrapper provides the actual
> interface to the outside world. But as there may be many properties I'd like to
> get away without the wrapper objects ...
>
> Thanks for any ideas!
> Stefan
>
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